1. Field of the Invention
The invention is directed to a fluid pressure damper, and more particularly to a flat tubular pressure damper for damping fluid pressure pulsations in fluid lines and to a fuel supply line embodying such a pressure line.
2. Description of the Prior Art
DE 44 31 770 A1 has disclosed a pressure pulsation damper for a fuel pump of an internal combustion engine which damps the pressure pulsations in the fuel produced by the fuel pump. The pressure pulsation damper is an elongated, thin-walled tube which is contained in a cage and is clamped and closed at the ends in order to form at least one chamber which contains a gas at a supra-atmospheric pressure. The chamber absorbs and damps the pressure pulsations and noise produced by the fuel pump by virtue of the fact that the chamber wall constituted by the tube deforms elastically and transmits the pulsations to the gas cushion inside the chamber. Due to the elastic deformation of the chamber and the resulting compression of the gas cushion, pulsation energy is lost, as a result of which the pressure pulsations are damped. The cross section of the chamber is constant along its longitudinal span and is small in comparison to this longitudinal span.
The known pressure pulsation damper has the disadvantage that due to its constant cross section, an effective damping is limited to a particular spectrum of excitation frequencies. Determining this spectrum and making corresponding structural and manufacturing adaptations of the pressure pulsation damper to the respective pulsations prevailing in the fuel, however, is time-consuming and expensive. On the other hand, because of the constant cross section of the pressure pulsation damper, there is a natural frequency, with corresponding harmonics. When the natural frequency or its multiple coincides with the excitation frequency of the pressure pulsations in the fuel or with the speed of the internal combustion engine, resonance pulsations with large oscillation amplitudes are produced, as a result of which the damping action of the pressure pulsation damper is sharply limited and undesirable noise is produced in the fuel system. Even if the pressure pulsation damper is designed so that its natural frequency lies outside the excitation range of the fuel system or the engine speed, even slight changes in the fuel system of the kind that occur in the course of a product""s life cycle, e.g. a change of the fuel line length or of the line material, the excitation spectrum can be shifted once again into the range of the resonance frequency.
A flat tubular damper for damping fluid pressure pulsations according to the invention has the advantage over the prior art that an effective damping is produced for a wide spectrum of pulsation excitation frequencies, which is achieved by means of a continuous or discrete changing of its cross section. The damping action of the flat tubular damper is no longer selectively limited to particular excitation frequencies since the individual sections with different cross sections react to different excitation frequencies. The flat tubular damper according to the invention can therefore be universally used for different fuel system configurations or fluid line system configurations. Since there is no longer a constant cross section, there is also no pronounced natural frequency that could give rise to resonance problems.
In a particularly preferable embodiment, the chamber is comprised of a thin-walled, originally cylindrical tubular body made of sheet steel, whose ends are closed and which is pressed flat along its longitudinal axis to different degrees lateral to the longitudinal axis. As a result, the flat tubular damper can be economically produced and is at the same time sturdy, durable, and reliable.